Russian space boffins have come up with a new reason to explain why duff Martian probe Phobos-Grunt fell out of the sky - cosmic rays.

The head of space agency Roscosmos said that an investigation into the short-lived spacecraft had discovered that radiation caused a glitch in the onboard computer system, state news agency RIA Novostireported.

"Two components of the onboard computer system were spontaneously rebooted and it switched into a standby mode," Vladimir Popovkin said. "The most likely reason [for this] is the impact of heavy charged space particles."

Popovkin and other Russian space sources had previously hinted that the probe, which became stranded in Earth's orbit after its engines failed to fire, had been taken out by "foreign influences", whether intentionally or not.

One source even went so far as to speculate that radiation from a US radar stationed on the Marshall Islands was to blame, although other Russian boffins almost immediately dismissed the idea as "far-fetched".

However, despite having ruled out evil US ray-guns as the cause of Phobos-Grunt's failures, Popovkin was still foisting some of the blame outside of Russia by saying that defective microchips imported illegally from abroad might have been part of the problem.

Those involved in the Phobos-Grunt project appear to be scrambling for some external reason why the mission may have failed, particularly since their president practically promised that heads will roll over the whole thing.

But scientists don't seem to think this latest excuse is any better than the US-megawatt-radar one. A source in the space industry told RIA Novosti a few hours after Popovkin's announcement of the findings that the idea that Phobos-Grunt hadn't had any protection from cosmic radiation was "ridiculous".

"The spacecraft was supposed to fly into the hostile environment of outer space, I simply can't believe they didn't consider this, " he said (translated by Google Translate).

'Get your gas to Mars!'

Meanwhile, Popovkin has also said that if Russia can't get in on the European Space Agency's (ESA) ExoMars action, it would consider trying Phobos-Grunt 2.

"We are holding consultations with the ESA about Russia’s participation in the ExoMars project… If no deal is reached, we will repeat the attempt [to launch a Phobos mission],” the Roscosmos chief said.

The ExoMars mission aims to send an orbital spacecraft, the ExoMars Trace Gas Orbiter, to Mars in 2016, followed by an ExoMars Rover two years later. The project started out as a joint venture between ESA and NASA, but the Americans later said they were ending their participation in the project and would no longer provide the Atlas rocket to launch the orbiter.

With NASA no longer able to afford the rocket and ESA lacking the funds even for the mission, not to mind a rocket, Roscosmos could solve the tetchy propulsion problem by providing one of its Proton launchers to get the craft going.

Roscosmos and ESA are due to discuss the possibilities for Russia's full membership in the ExoMars mission this month. ®